Podcast
Questions and Answers
Which of the following is NOT considered a component of the first line of defence?
Which of the following is NOT considered a component of the first line of defence?
What is the primary role of lysozymes found in saliva?
What is the primary role of lysozymes found in saliva?
Which of the following best describes the innate immunity?
Which of the following best describes the innate immunity?
Which function is NOT attributed to antimicrobial peptides (AMPs)?
Which function is NOT attributed to antimicrobial peptides (AMPs)?
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What property of the skin contributes to its effectiveness as a barrier against pathogens?
What property of the skin contributes to its effectiveness as a barrier against pathogens?
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What characteristic of normal microflora contributes to the first line of defence?
What characteristic of normal microflora contributes to the first line of defence?
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What is the role of the coughing and sneezing reflexes in the immune system?
What is the role of the coughing and sneezing reflexes in the immune system?
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What distinguishes acquired immunity from innate immunity?
What distinguishes acquired immunity from innate immunity?
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What effect does the outer layer of dead keratinocytes have on pathogens?
What effect does the outer layer of dead keratinocytes have on pathogens?
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Which type of cell is specifically targeted by antimicrobial peptides due to their membrane structure?
Which type of cell is specifically targeted by antimicrobial peptides due to their membrane structure?
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Study Notes
First Line of Defense
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Physical Barriers:
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Skin: A multi-layered barrier, the outer layer composed of dead keratinocytes, effectively blocking pathogen entry. The dermis contains immune cells. The slightly acidic pH, high NaCl concentration, and dryness contribute to its microbial resistance. Constant shedding of the outer skin layers removes potential pathogens.
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Epithelial linings: Protective barriers lining the nose, throat, and intestines. Mucus and cilia trap and remove pathogens. Coughing, sneezing, and vomiting expel pathogens.
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Normal microflora: Beneficial microorganisms compete with pathogens for resources, preventing colonization.
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Chemical Barriers:
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pH: High acidity in the stomach and low pH on the skin limit pathogen survival.
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Saliva, tears, and other secretions: Contain antimicrobial substances such as:
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Lysozymes: Enzymes that break down bacterial cell walls. They cleave the peptidoglycan, weakening the cell wall and causing bacterial lysis due to osmotic pressure.
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Antimicrobial peptides (AMPs): Short peptides with a wide range of antimicrobial activity. Mechanisms include membrane disruption and sequestration of essential nutrients like zinc.
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Examples include psoriasin, defensins, and lactoferricin.
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Defensins: Positively charged peptides (alpha and beta types) that create pores in bacterial membranes, leading to cell death. Lactoferricin chelates iron, making it unavailable to pathogens.
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Psoriasin targets Gram-negative bacteria, demonstrating selectivity.
Innate Immunity
- Rapid and nonspecific response: This immediate immune response involves various cells, including macrophages, natural killer (NK) cells, and dendritic cells.
Acquired Immunity
- Slow, long-lasting, and highly specific response: Involves lymphocytes (B cells and T cells).
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Description
Explore the essential physical and chemical barriers that form the first line of defense in the immune system. This quiz covers the roles of skin, epithelial linings, normal microflora, and antimicrobial substances in protecting against pathogens. Test your knowledge on how these factors contribute to our overall immunity.
